The NestedPropertyInfo is used when there is more than one setter for the property and no getter to resolve which one should get used. Instead it tries to guess (using isAssignable) at runtime based on what you pass to the api If the parameter is not assignable to any, it throws that exception. e.g. | public void setSomething(Collection c); | public void setSomething(String s); | is "something' a Collection or a String? The answer is it depends what "value" you pass to PropertyInfo.set(Object bean, Object value). View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4098871#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...